I. Field of the Invention
This invention relates to bonding or sealing apparatus for thermoplastic articles and more specifically to the novel design of a combined rotary and linear drive mechanism for transporting the workpieces incrementally from a loading station to a heating station and from there to a bonding station where the articles to be joined are subjected to a compressive force following the heating step. The system of the present invention adapts itself to the use of stationary platens, although if the geometry of the work requires, modest movement of the platens may be undertaken without adversely affecting the speed of operation of the entire system.
II. Description of the Prior Art
Many different bonding or sealing machines for joining thermoplastic surfaces together are known in the art. It is a common practice to transport the articles to be bonded from a work station, through a heating zone and to a bonding zone where the parts to be joined are subjected to substantial compressive forces during the period that the thermoplastic articles are cooled. For example, there is disclosed in the Karpowicz U.S. Pat. No. 2,886,931 a machine for forming and sealing plastic packages and which utilizes incrementally rotatable roller members for advancing thermoplastic material to a bonding station where a heated segment of the rotary members effects the bond or seal. A review of the device described in the Karpowicz patent immediately shows that it is quite complex in terms of the drive mechanism employed and the various electromechanical controls used to drive, form, heat and bond the surfaces to be joined. Then too, the apparatus disclosed in the aforementioned Karpowicz patent is only suitable for bonding sheet-like materials together and is, thus, somewhat limited in its application.
Still other prior art devices of a similar type are set forth in the Akke U.S. Pat. No. 3,759,011, the Kath U.S. Pat. No. 3,269,088 and the Hansen U.S. Pat. No. 3,465,496. In each of these arrangements, rotary members driven in opposite directions and intersecting generally along a line of contact, are used to advance the materials to be joined and to apply the required heat and compressive forces to effect bonding. Again, each of these prior art machines tends to be somewhat complex in its construction and is suitable only for use with continuous sheet materials.